DNA nanostructures from palindromic rolling circle amplification for the fluorescent detection of cancer-related microRNAs

Herein, DNA nanostructures were prepared via a palindromic padlock probe-based rolling circle amplification (called P-RCA) and then employed to implement the sensitive and specific detection of let-7a miRNA extracted from cancer cells without chemical modification. The presence of target let-7a miRNA as a polymerization primer can trigger the P-RCA process, generating a long tandemly repetitive DNA strand. The resulting products can fold into nanostructures via self-hybridization of palindromic regions and possess numerous double-stranded fragments. In this case, the strong fluorescent signal is detected upon exposure to SYBR Green I. As a result, in homogeneous solution, target miRNA can be detected down to 6.4 pM with a wide dynamic range. A high specificity was demonstrated by the excellent discrimination between let-7 miRNA family members, while the applicability of this sensing system in complex biological environments was confirmed by the analysis of target miRNAs extracted from HeLa cells. It should be noted that increasing numbers of palindromic fragments in padlock probe further increases signal amplification efficiency. The experimental results indicate that the newly proposed P-RCA DNA nanostructures have potential to become a promising analytical platform in biomedical research and clinical diagnosis for the miRNA detection with high sensitivity and good specificity.